arXiv subjects

Yves Dumont

Publications and source records attributed to Yves Dumont.

24 records · Page 2Linked to original sources

arXiv2018

On the use of the sterile insect technique or the incompatible insect technique to reduce or eliminate mosquito populations

Vector control is critical to limit the circulation of vector-borne diseases like chikungunya, dengue or zika which have become important issues around the world. Among them the Sterile Insect Technique (SIT) and the Incompatible Insect Technique (IIT) recently aroused a renewed interest. In this paper we derive and study a minimalistic mathematical model designed for Aedes mosquito population elimination by SIT/IIT. Contrary to most of the previous models, it is bistable in general, allowing simultaneously for elimination of the population and for its survival. We consider dierent types of releases (constant, periodic or impulsive) and show necessary conditions to reach elimination in each case. We also estimate both sucient and minimal treatment times. Biological parameters are estimated from a case study of an Aedes polynesiensis population, for which extensive numerical investigations illustrate the analytical results. The applications of this work are twofold: to help identifying some key parameters that may need further eld investigations, and to help designing release protocols.

math.DS↗

arXiv2018

Redox reaction enhanced Schottky contact at a \LNO{}(001)/Al interface

Emergent phenomena at interfaces between oxides and metals can appear due to charge transfer and mass transport that modify the bulk properties. By coating the metallic oxide LaNiO$_3$ by aluminium, we fabricated a junction exhibiting a diode-like behaviour. At the equilibrium, the interface is insulating. The metallic behaviour can be recovered by applying a voltage drop across the junction in one polarity only. The electrical properties in direct and reverse bias are investigated. The observed electro-resistive effect rises up to $10^5$ \% and can be interpreted in terms of (i) a spontaneous redox reaction occurring at the interface and (ii) its reversal induced by charge injection in direct bias.

cond-mat.mtrl-sci↗

arXiv2018

Effect of rainfall and fire frequency on tree--grass dynamics: Capturing the forest--savanna distributions along biogeographic gradients

In this work, we improve a previous minimalistic tree-grass savanna model by taking into account water availability, in addition to fire, since both factors are known to be important for shaping savanna physiognomies along a climatic gradient. As in our previous models, we consider two nonlinear functions of grass and tree biomasses to respectively take into account grass-fire feedbacks, and the response of trees to fire of a given intensity. The novelty is that rainfall is taken into account in the tree and grass growth functions and in the biomass carrying capacities. Then, we derive a qualitative analysis of the ODE model, showing existence of equilibria, and studying their stability conditions. We also construct a two dimension bifurcation diagram based on rainfall and fire frequency. This led to summarize different scenarios for the model including multi-stabilities that are proven possible. Next, to bring more realism in the model, pulsed fire events are modelled as part of an IDE (Impulsive differential Equations) system analogous to the ODE system. Numerical simulations are provided and we discuss some important ecological outcomes that our ODE and IDE models are able to predict. Notably, the expansion of forest into tree-poor physiognomies (grassland and savanna) is systematically predicted when fire return period increases, especially in mesic and humid climatic areas.

q-bio.PE↗

arXiv2017

Bismuth iron garnet Bi3Fe5O12: a room temperature magnetoelectric material

The possibility to control the magnetic properties of a material with an electric field at room temperature is highly desirable for modern applications. Moreover, a coupling between magnetic and electric orders within a single material presenting a wide range of exceptional physical properties, such as bismuth iron garnet (BIG), may lead to great advances in the field of spintronic applications. In particular, the combination of the magnetoelectric (ME) coupling with the low damping of spin waves in BIG can allow the control and manipulation of spin waves by an electric field in magnonic devices. Here we report the unambiguous observation of linear magnetoelectric coupling above 300 K in BIG using ferromagnetic resonance technique with electric field modulation. The measured coupling value is comparable with that observed for prototypal magnetoelectric Cr2O3. On the basis of our experimental results, the strength of this linear ME coupling is directly linked to the presence of bismuth ions inducing strong spin orbit coupling and to the appearance of local magnetic inhomogeneities related to the magnetic domain structure. The unprecedented combination of magnetic, optical and magnetoelectrical properties in BIG is expected to trigger significant interest for technological applications as well as for theoretical studies.

cond-mat.mtrl-sci↗

arXiv2017

Tuning the Electronic Properties of LAO/STO Interfaces by Irradiating LAO Surface with Low-Energy Cluster Ion Beams

We have investigated the effects of low-energy ion beam irradiations using argon clusters on the chemical and electronic properties of LaAlO3/SrTiO3 (LAO/STO) heterointerfaces by combining X-ray photoelectron spectroscopy (XPS) and electrical transport measurements. Due to its unique features, we show that a short-time cluster ion irradiation of the LAO surface induces indirect modifications in the chemical properties of the buried STO substrate, with (1) a lowering of Ti atoms oxidation states (from Ti4+ to Ti3+ and Ti2+) correlated to the formation of oxygen vacancies at the LAO surface and (2) the creation of new surface states for Sr atoms. Contrary to what is observed by using higher energy ion beam techniques, this leads to an increase of the electrical conductivity at the LAO/STO interface. Our XPS data clearly reveal the existence of dynamical processes on the titanium and strontium atoms, which compete with the effect of the cluster ion beam irradiation. These relaxation effects are in part attributed to the diffusion of the ion-induced oxygen vacancies in the entire heterostructure, since an increase of the interfacial metallicity is also evidenced far from the irradiated area. These results demonstrate that a local perturbation of the LAO surface can induce new properties at the interface and in the entire heterostructure. This study highlights the possibility of tuning the electronic properties of LAO/STO interfaces by surface engineering, confirming experimentally the intimate connection between LAO surface chemistry and electronic properties of LAO/STO interfaces.

cond-mat.str-el↗

arXiv2016

Mathematical model for pest-insect control using mating disruption and trapping

Controlling pest insects is a challenge of main importance to preserve crop production. In the context of Integrated Pest Management (IPM) programs, we develop a generic model to study the impact of mating disruption control using an artificial female pheromone to confuse males and adversely affect their mating opportunities. Consequently the reproduction rate is diminished leading to a decline in the population size. For more efficient control, trapping is used to capture the males attracted to the artificial pheromone. The model, derived from biological and ecological assumptions, is governed by a system of ODEs. A theoretical analysis of the model without control is first carried out to establish the properties of the endemic equilibrium. Then, control is added and the theoretical analysis of the model enables to identify threshold values of pheromone which are practically interesting for field applications. In particular, we show that there is a threshold above which the global asymptotic stability of the trivial equilibrium is ensured, i.e. the population goes to extinction. Finally we illustrate the theoretical results via numerical experiments.

math.DS↗